Fully buried color filter array of image sensor

ABSTRACT

An image sensor includes a substrate. An array of photodiodes is disposed in the substrate. A plurality of spacers is arranged in a spacer pattern. At least one spacer of the plurality of spacers has an aspect ratio of 18:1 or greater. A buffer layer is disposed between the substrate and the spacer pattern. An array of color filters is disposed in the spacer pattern.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional of U.S. application Ser. No.16/539,931, filed on Aug. 13, 2019, which is hereby incorporated byreference in its entirety.

BACKGROUND INFORMATION Field of the Disclosure

The present invention relates generally to color filters, and morespecifically, to color filter arrays of image sensors.

Background

Color image sensors include color filter arrays. Each color filter inthe array of color filters may allow only one color of light to passthrough to a sensor. A color filter array may include side walls betweentwo adjacent color filters that isolate each color filter fromneighboring color filters of the array of color filters. However, theseside walls may take up a substantial amount of space and hurt colorarray filter occupancy density.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention aredescribed with reference to the following figures, wherein likereference numerals refer to like parts throughout the various viewsunless otherwise specified.

FIGS. 1A-1I illustrate an example of a cross section view of a fullyburied color filter array at different steps of the formation of thearray of color filters in accordance with the teachings of the presentinvention.

FIGS. 2A-2H illustrate an example of a cross section view of a fullyburied color filter array at different steps of the formation of thearray of color filters in accordance with the teachings of the presentinvention.

FIGS. 3A-3C illustrate example top down views of a fully buried colorfilter array at different steps of the formation of the array of colorfilters in accordance with the teachings of the present invention.

FIG. 4 is a flow diagram illustrating processing steps to fabricate oneexample of a fully buried color filter array device in accordance withthe teachings of the present invention.

FIG. 5 is a diagram illustrating one example of an imaging system withfully buried color filter array in accordance with the teachings of thepresent invention.

Corresponding reference characters indicate corresponding componentsthroughout the several views of the drawings. Skilled artisans willappreciate that elements in the figures are illustrated for simplicityand clarity and have not necessarily been drawn to scale. For example,the dimensions of some of the elements in the figures may be exaggeratedrelative to other elements to help to improve understanding of variousembodiments of the present invention. Also, common but well-understoodelements that are useful or necessary in a commercially feasibleembodiment are often not depicted in order to facilitate a lessobstructed view of these various embodiments of the present invention.

DETAILED DESCRIPTION

Examples directed to arrays of color filters, and methods forfabricating the same using a sacrificial replacement layer are disclosedherein. In the following description, numerous specific details are setforth to provide a thorough understanding of the examples. One skilledin the relevant art will recognize, however, that the techniquesdescribed herein can be practiced without one or more of the specificdetails, or with other methods, components, materials, etc. In otherinstances, well-known structures, materials, or operations are not shownor described in detail in order to avoid obscuring certain aspects.

Reference throughout this specification to “one example” or “oneembodiment” means that a particular feature, structure, orcharacteristic described in connection with the example is included inat least one example of the present invention. Thus, the appearances ofthe phrases “in one example” or “in one embodiment” in various placesthroughout this specification are not necessarily all referring to thesame example. Furthermore, the particular features, structures, orcharacteristics may be combined in any suitable manner in one or moreexamples.

Throughout this specification, several terms of art are used. Theseterms are to take on their ordinary meaning in the art from which theycome, unless specifically defined herein or the context of their usewould clearly suggest otherwise. It should be noted that element namesand symbols may be used interchangeably through this document (e.g., Sivs. silicon); however, both have identical meaning.

Arrays of color filters with good photodiode isolation cause thephotodiodes disposed below the array of color filters to be moreaccurate. Side walls isolating individual color filters in the array ofcolor filters allow the array of color filters to have good photodiodeisolation. However, the side walls formed by standard photolithographymethods can take up a significant amount of space and hurt the occupancydensity of the array of color filters.

FIGS. 1A-1I illustrate an example of a cross section view of a fullyburied color filter array at different steps of the formation of thearray of color filters in accordance with the teachings of the presentinvention. FIG. 1A illustrates an image sensor device with a substrate110 including a plurality of photodiodes 115 and a buffer layer 120disposed on the substrate 110. The substrate 110 may be a semiconductormaterial such as silicon substrate or a silicon substrate doped withimpurities e.g., p-type doped silicon substrate or n-type doped siliconsubstrate. The photodiodes 115 may be formed in the substrate 110. Inone embodiment, the photodiodes 115 may be n-type doped photodiodesformed by implanting and/or diffusing n-type impurities e.g., arsenic orphosphorous while the substrate 110 may be p-type doped siliconsubstrate. In another embodiment, the photodiodes 115 may p-type dopedphotodiode formed by implanting and/or diffusing p-type impurities e.g.,boron while the substrate 110 may be n-type doped silicon substrate. Thebuffer layer 120 may be an oxide such as silicon dioxide or anothermaterial which is transparent to light in the visible spectrum. Each ofthe photodiodes 115 may generate photo-induced charge in response toincident light received.

FIG. 1B illustrates the device of FIG. 1A with a layer of sacrificialmaterial 130 formed on the buffer layer 120. The layer of sacrificialmaterial 130 may be formed by depositing chemical vapor deposition. Inone embodiment, the layer of sacrificial material 130 may be flattenedby a chemical mechanical polishing (CMP) process. The sacrificialmaterial may be a material which may be removed with a wet etchingprocess, including but not limited to carbon-based material, oxidematerial, nitride material, silicon-based material. The sacrificialmaterial may be a material which can be patterned by a dry etchingprocess. As illustrated in FIG. 1B, the layer of sacrificial material130 may be formed as a flat layer of uniform thickness. The layer ofsacrificial material 130 should be made of a material that when removedby a wet etching process will not cause the buffer layer 120 to besubstantially removed as well. For example, if the buffer layer 120 issilicon dioxide, the layer of sacrificial material 130 should not alsobe silicon dioxide. Restated, the buffer layer 120 and the layer ofsacrificial material 130 may be made of different materials where thesacrificial material is etch selective from the buffer layer 120. Inother words, the material for forming the layer of sacrificial material130 may be selected from materials having different etching rate thanthe material for forming the buffer layer 120. In one embodiment, thelayer of sacrificial material may be made from nitride material and thebuffer layer 120 may be made from silicon dioxide.

FIG. 1C illustrates the device of FIG. 1B with parts of the layer ofsacrificial material 130 removed to form a pattern of sacrificialmaterial 135. As will be described in greater detail below, the patternof sacrificial material 135 may be a “checkerboard” pattern. The patternof sacrificial material 135 may be formed by patterning and dry etchingthe layer of sacrificial material 130 according to the “checkerboard”pattern. In an embodiment, the pattern of sacrificial material 135 mayform blocks of sacrificial material 136. Each one of the blocks ofsacrificial material 136 may have a rectangular prism shape such thatthe block of sacrificial material has four sides of about equal length.As illustrated in FIG. 1C, the blocks of sacrificial material 136 arespaced apart in one direction by about the length of one of the sides ofthe blocks of sacrificial material 136. In other embodiments, the blocksof sacrificial material 136 may have 4 sides not having equal length.The shape and the size of the blocks of sacrificial material may dependupon the desired sizes and shape for the spacers and the color filtersfor the imaging sensor device. Each block of sacrificial material 136may cover one photodiode 115 and be centered on the respectivephotodiode 115. Alternatively, each block of sacrificial material maycover multiple photodiodes 115. The thickness or height of the blocks ofsacrificial material 136 may be configured based on the desiredthickness or height for the spacer.

FIG. 1D illustrates the device of FIG. 1C with a spacer pattern 140formed on the sides of the blocks of sacrificial material 136. Thespacer pattern 140 may be formed of individual spacers 145 formed onindividual sides of the blocks of sacrificial material 136, for exampleby atomic layer deposition (ALD) or chemical vapor deposition (CVD). Inone embodiment, the spacers 145 may be formed as a continuous spacergrid. In one embodiment, the width of each individual spacer 145 mayrange between 0.01-0.1 um. The width of the spacers 145 may be definedby the space between the blocks of sacrificial material 136 and may bethinner than the minimum critical dimension (CD) of the lithographicpatterning and etching process. In one embodiment, the individualspacers 145 may be less than or equal to 0.05 μm thick. The individualspacers 145 may come in contact with each other at points betweencorners of the blocks of sacrificial material 136. The spacer pattern140 may be thicker than 0.05 μm at the corners where the spacers 145connect. Restated, the aspect ratio (height to width ratio) of thespacers 145 may be up to 18:1 or even greater.

The spacer pattern 140 is made of a spacer material that has etchselectivity against the sacrificial material and the buffer layer 120.The spacer material may also have a refractive index as low as of 1.3 oreven less. The material for forming the spacers 145 may be selectedbased on the applications of the image sensor device or the opticalperformance required for the image sensor device. In one embodiment,each of the spacers 145 may be a single or multilayer-stack structure.In one embodiment, the material for forming the spacers 145 may be oxidematerial, nitride material, or a material with low index of refraction(e.g., a material having index of refraction lower than 1.3). In anotherembodiment, the material for forming the spacers 145 may be a materialwith high reflectivity, such as metal. In one embodiment, the spacer maybe formed by a combination of metal and dielectric material, for exampleformed of metal material (e.g., tungsten or aluminum) enclosed by alayer of dielectric material e.g., silicon oxide

In an embodiment, the process of forming the spacers 145 (discussedbelow) causes a first side of the spacer 145 facing away from thepattern of sacrificial material to have a slated portion near the top ofthe spacer 145, which is not completely vertical and slanted toward theblock of sacrificial material. Accordingly, the first side has a firstslant. A second side of the spacer 145 facing the block of sacrificialmaterial will be more vertical or may be slightly slanted away from thevertical portion of the spacer 145. Accordingly, the second side has asecond slant that is different from the first slant. Restated, thesecond side of the spacer 145 facing the block of sacrificial materialmay conform to the shape of the block of sacrificial material and have adifferent slant than the first side of the spacer 145 facing away fromthe block of sacrificial material.

FIG. 1E illustrates the device of FIG. 1D with the pattern ofsacrificial material 135 removed. When the sacrificial material isremoved, a free standing spacer pattern 140 remains. As will be furtherexplained below, the free standing spacer pattern 140 defines firstopenings 148 and second openings 149 between four spacers 145. Each ofthe first openings 148 is defined by four first sides of spacers 145.Each of the second openings 149 is defined by four second sides of thespacers 145. Restated, the first openings 148 are adjacent only to firstsides of the spacers 145, and the second openings 149 are adjacent onlyto second sides of the spacers 145. The first openings 148 will allow inslightly more light than the second openings 149 based on the geometryof the tops of the spacers 145.

FIG. 1F illustrates the device of FIG. 1E with an array of color filters150 formed by depositing color filter material in the first and secondopenings 148, 149. In one embodiment, the color filters array 150 may bea Bayer filter mosaic with a pattern of four color filters (two greensfilters, one red filter, and one blue filter) clustered togetherrepeating throughout the array of color filters. In one embodiment, thecolor filter material may include red color filter material, blue colorfilter material, and green color filter material. In one example, Bayerpattern filter mosaic is used and the first openings 148 are filled withthe red and blue color filters to slightly improve the sensitivity ofthe red and blue photodiodes compared to the green photodiodes. Inanother example, the Bayer pattern filter mosaic is used and the firstopenings 148 are filled with the green color filters. In anotherembodiment, the array of color filters 150 may include a differentpattern of color filters, such as CMYK and the color filter material maybe comprised of cyan color filter material, magenta color filtermaterial, and yellow color filter material. The specific arrangement ofcolor filters for the array of color filters 150 may depend on theapplications of the image sensor device. It would be appreciated bythose skilled in the art that the material for forming color filters mayhave an index of refraction that is higher than the correspondingspacers 145 formed in between and the buffer layer 120. Alternative, thematerial selected for the spacers 145 may have index of refraction lowerthan the color filter material.

FIG. 1G illustrates the device of FIG. 1F with an array of microlenses160 formed on the array of color filters 150. The microlenses 160 areconfigured to focus incident light to the respective photodiodes 115. Inone embodiment, the microlenses 160 may be made of a microlens materialsuch as polymer. The microlenses 160 may be domed, or otherwise shapedto operate as a lens based on a difference in refractive index from theair to the microlens material. The curvature of each microlens may beconfigured based on the required optical performance (e.g., focallength) for the respective photodiode 115.

FIG. 1G illustrates an image sensor device with fully buried colorfilter array. The substrate 110 has an array of photodiodes 115 disposedin the substrate 110. Buffer layer 120 is formed on the substrate 110.Spacers 145 form a spacer pattern 140. The spacer pattern 140 is formedon the buffer layer 120 such that the buffer layer 120 is between thespacers 145 and the substrate 110. The array of color filters 150 isdisposed within the first and second openings 148, 149 of the spacerpattern 140 such that the array of color filters 150 is disposed in thespacer pattern 140.

The height of spacers 145 may be configured based on the desired opticalperformance of color filter and microlens array. In the embodiment ofFIG. 1G, the color filters in the array of color filter 150 may have aheight less than a height of the spacers 145. In another embodiment, thecolor filters in the array of color filter 150 may have a height same asa height of the spacers 145 as illustrated by FIG. 1H. In anotherembodiment, the color filters in the array of color filter 150 may havea height greater than the height of the spacers 145 as illustrated byFIG. 1I.

As pixels continue to shrink, the area used to ensure color filterisolation becomes more important. Examples in accordance with theteachings of the present invention provide significant advantages inboth color filter isolation and density. The spacers 145 provideimproved color filter isolation to the array of color filters 150. Inone example, the spacers 145 are formed of a material having arefractive index lower than a refractive index of each one of the colorfilters of the array of color filters 150. This material property of thespacers 145 and the array of color filters 150 causes photons to reflectoff the spacers 145 rather than pass through the spacers 145. Thus, thecolor filters are better isolated from light passing through theneighboring color filters and color filter isolation is improved evenwith a thin spacer 145.

The image sensor device can have the advantage of having tall and thinspacers 145 between the color filters, which prevent light coming from adirection other than a top side of the device from being directed intothe photodiode 115. Thus, the spacers 145 prevent corruption of thephotodiode output. The thin spacers 145 also provide the advantage ofnot occupying an excessive amount of the area of the fully buried colorfilter array when viewed from above. Photodiodes 115 require a minimumamount of light to sense properly an incident light source. Thus,photodiodes 115 need a certain amount of area to collect light using themicrolens 160 to operate properly. The amount of area needed isdependent on the lighting conditions, among other factors. The smallarea of the spacers 145 when viewed from above allows more photons topass through the microlenses 160 to the photodiodes 115 rather thancolliding with the spacers 145 and thus allows the array of colorfilters 150 and photodiodes 115 to take maximum effective area of thearray and have better quantum efficiency. The height and isolationeffects of the spacers 145 also provides for better angular response bythe image sensor.

FIGS. 2A-2H illustrate another example of a cross section view of afully buried color filter array at different times during fabrication ofthe fully buried color filter array in accordance with the teachings ofthe present invention. FIG. 2A illustrates an image sensor devicesimilar to that of FIG. 1A. FIG. 2A illustrates a pattern of supportmaterial 205 disposed on the buffer layer 220. The buffer layer 220 isdisposed on a substrate 210 including a plurality of photodiodes 215.

The pattern of support material 205 may be metal or a metalloid such astungsten or aluminum. The pattern of support material 205 should be amaterial that is etch selective from the buffer layer 220 and a layer ofsacrificial material 230 (discussed below). In one embodiment, thesupport material 205 may further direct incident light to the respectivephotodiodes 205 by reflection or refraction, such that optical crosstalk between neighboring photodiodes may be suppressed.

FIG. 2B illustrates the image sensor device of FIG. 2A with an adhesivelayer 208 on the pattern of support material 205. The adhesive layer 208may be titanium nitride (TiN). The adhesive layer 208 may cover a topsurface of the pattern of support material 205. The adhesive layershould be etch selective from the buffer layer 220 and the layer ofsacrificial material 230 (discussed below).

FIG. 2C illustrates the image sensor device of FIG. 2B with the layer ofsacrificial material 230 formed on the pattern of support material 205,the adhesive layer 208 and the buffer layer 220. The layer ofsacrificial material 230 may be made of the same material and formed bythe same process as discussed with relation to the layer of sacrificialmaterial 130.

FIG. 2D illustrates the image sensor device of FIG. 2C with a pattern ofsacrificial material 235 etched from the layer of sacrificial material235. The pattern of sacrificial material 235 may include blocks ofsacrificial material 236. The blocks of sacrificial material 236 may becentered in an opening in a grid formed by the pattern of supportmaterials 205. As such, each block of sacrificial material 236 is incontact with four portions of the grid that is formed by the pattern ofsupport materials 205, which define the opening in the pattern ofsupport material 205. Each block of sacrificial material 236 may coverabout half of the four portions of the pattern of support material 205and the adhesive layer on top of the four portions of the pattern ofsupport material 205.

FIG. 2E illustrates the image sensor device of FIG. 2D with a spacerpattern 240 formed on side walls of the pattern of sacrificial material235. The spacer pattern 240 may be disposed on top of the adhesive layer208 and pattern of support material 205 in the center of the adhesivelayer. The spacers 245 forming the spacer pattern 240 may be made of thesame material, have the same properties, and be formed in the same wayas disclosed above with relation to the spacer pattern 140 except thatthe spacer pattern 240 is formed on the adhesive layer 208. In oneembodiment, the spacer pattern 240 may be in a form of a continuouspattern, thus the spacers 245 can be formed as a continuous spacer grid.

A height of the spacer pattern 240 may be limited by the strength of thematerial used to form the spacer pattern 240 and/or the process offorming the spacers 245. By forming the spacer pattern 240 on theadhesive layer 208 on the pattern of support material 205 rather thandirectly on the buffer layer 220, the height of the first and secondopenings 248, 249 formed by the combination of the pattern of supportmaterial 205, adhesive layer 208, and spacer pattern 240 may extendfurther from the buffer layer 220 than the first and second openings148, 149 in the spacer pattern 140 from the buffer layer 120.

FIG. 2F illustrates the image sensor device of FIG. 2E with the patternof sacrificial material 235 removed. The pattern of sacrificial material235 may be removed by the same process as described below with relationto the pattern of sacrificial material 135.

FIG. 2G illustrates the image sensor device of FIG. 2F with an array ofcolor filters 250 disposed in the first and second openings 248, 249.Each color filter 250 is formed between two adjacent spacers 245. Thearray of color filters 250 may be formed of the same material, have thesame properties, and be formed in the same way as the array of colorfilters 150, except that the array of color filters 250 may have aheight less, the same, or greater than the height of the spacer 245.Therefore, the array of color filters 250 will have a height greater, orless than or equal to the combined height of the spacers 245, theadhesive layer 208, and the pattern of support material 205. Restated,the spacer pattern 240 on the adhesive layer 208 and pattern of supportmaterial 205 may extend further from the buffer layer 220 than the arrayof color filters 250.

FIG. 2H illustrates the device of FIG. 2G with microlenses 260 formed onthe array of color filters 250. The microlenses 260 may be formed of thesame material, have the same properties, and be formed in the same wayas the microlenses 160. The focal lengths of the each microlens 260 maydepend upon on the height of color filters 250. As such, the height ofthe array of color filters 250 may be configured based on the desiredoptical performance for the image sensor device.

FIG. 2H illustrates an image sensor device with a fully buried colorfilter array. The substrate 210 has an array of photodiodes 215 disposedin the substrate 210. Buffer layer 220 is formed on the substrate 210. Apattern of support material 205 is formed on the buffer layer 220 suchthat the buffer layer 220 is between the pattern of support material 205and the substrate 210. An adhesive layer is formed on the pattern ofsupport material 205 such that the pattern of support material and thebuffer layer 220 are between the adhesive layer 208 and the substrate210. Spacers 245 form a spacer pattern 240. The spacer pattern 240 isformed on the buffer layer such that the buffer layer 220, pattern ofsupport material 205 and adhesive layer 208 are between the spacers 245and the substrate 210. The array of color filters 250 is disposed withinthe first and second openings 248, 249 of the spacer pattern 240 suchthat the array of color filters 150 is disposed in the spacer pattern240 and the pattern of support material 205.

The embodiment shown in FIG. 2H provides even greater color filterisolation than the embodiment shown in FIG. 1G, while providing similarcolor filter array occupancy density. Some photo image sensors mayrequire very high color filter isolation and large color filteroccupancy density. However, the height of spacers 145 for a giventhickness may be limited by the strength of the spacer material suchthat the spacer height needed for color filter isolation requires aspacer thickness too great for the required color filter array occupancydensity. This problem may be solved by placing the spacers 245 on thepattern of support material 205 and adhesive layer 208. This increasesthe distance which the spacers 245 extend from the buffer layer 220without increasing the area taken up by the spacer at the top of thearray of color filters 250. The microlens 260 focuses light toward acenter of the color filter toward a photodiode 215 disposed below thecenter of the base of color filter. Accordingly, the extra area taken upby the pattern of support material 205 at the bottom of the color filterdoes not have much effect on the photodiode 215, and the array of colorfilters 250 may maintain the same density as the array of color filters150 illustrated in FIG. 1G.

FIGS. 3A-3C illustrate example top down views of a fully buried colorfilter array at different times during the fabrication of the fullyburied color filter array. FIG. 3A illustrates an example view of thepattern of sacrificial material 335 and additional sacrificial materialpattern 338. FIG. 1C may be an example of the device of FIG. 3A alongthe line Ia-Ia′. The additional sacrificial material pattern 338 may bemade of the same material, have the same properties, and be formed in asimilar manner to the pattern of sacrificial material 335. The blocks ofsacrificial material 336 making up the pattern of sacrificial material335 may form a “checkerboard” pattern. The spaces between the blocks ofsacrificial material 336 forming the pattern of sacrificial material 335may be about the same size and dimensions as the blocks of sacrificialmaterial 336. The additional sacrificial material pattern 338 may beformed to assist in forming spacers 345 on the periphery of the spacerpattern 340. The additional sacrificial material pattern 338 does notneed to form blocks with the same dimensions as the blocks ofsacrificial material 336 forming the pattern of sacrificial material335, but only need to define a side wall on which a spacer 345 may beformed in order to complete the spacer pattern 340. Accordingly theblocks of sacrificial material 339 forming the additional sacrificialmaterial pattern 338 may have a different shape than the blocks ofsacrificial material 336 forming the pattern of sacrificial material335.

FIG. 3B illustrates an example view of the pattern of sacrificialmaterial 335 and the additional sacrificial material pattern 338 withthe spacer pattern 340 formed on the sides of the pattern of sacrificialmaterial 335. The spacer pattern 340 may form a continuous spacer grid.FIG. 1D may be an example of the device of FIG. 3B along the lineIb-Ib′. The spacers 345 may be formed on sides of the additionalsacrificial material pattern 338 in the same manner as the spacers 345formed on the side walls of the pattern of sacrificial material 335.

FIG. 3C illustrates an example view of the spacer pattern 340 with thepattern of sacrificial material 335 and the additional sacrificialmaterial pattern 338 removed. FIG. 1E may be an example of the device ofFIG. 3C along the line Ic-Ic′.

FIG. 4 is a flow diagram illustrating processing steps to fabricate oneexample of a fully buried color filter array device in accordance withthe teachings of the present invention. The process of FIG. 4 may beperformed on a devices such as the device shown in FIG. 1A. Processblock 410 shows the process may begin by forming a pattern of supportmaterial 205 and an adhesive layer 208 on the device.

The pattern of support material 205 may be formed by depositing thesupport material then etching away some of the support material. Forexample, the support material may be deposited as a blanket layer ofaluminum, and then the blanket layer of aluminum may be etched to formthe pattern of support material 205. The pattern of support material maydefine a square or rectangular grid matching the spacer pattern 340shown in FIGS. 3B-3C, but with wider “lines” in the grid.

In an embodiment, the adhesive layer 208 may be formed on top of thepattern of support material 205 by a vapor deposition process. A nitridehard mask is formed on the adhesive layer 208 on top of the pattern ofsupport material 205, and an etching process may remove adhesivematerial that was deposited in locations not covered by the nitride hardmask. The nitride hard mask may then be removed. The adhesive layer 208may also be formed by any other process that deposits the adhesive layer208 on top of the pattern of support material 205 and not the bufferlayer 220. Forming the pattern of support material 205 and the adhesivelayer 208 is optional and may not be performed.

Process block 420 shows that the pattern of sacrificial material 135 or235 is formed. If the pattern of support material 205 and an adhesivelayer 208 on the device are formed, then a layer of sacrificial material230 may be formed on top of the pattern of support material 205, anadhesive layer 208, and the buffer layer 220. Otherwise, the layer ofsacrificial material 130 may be formed on the buffer layer 120.

The layer of sacrificial material 130 or 230 may be formed bydeposition, for example by chemical vapor deposition (CVD). In oneembodiment, a chemical mechanical polishing or planarization process maybe applied after the deposition of layer of sacrificial material 130 or230 to smooth or flattening the surface of layer of sacrificial material230. The layer of sacrificial material 130 or 230 may be etched by a dryetching process in order to form the pattern of sacrificial material135. The pattern of sacrificial material 235 may be etched using thesame process as described with relation to the pattern of sacrificialmaterial 135.

Process block 430 shows that the spacer pattern 140 or 240 is formed onthe side walls of the sacrificial material. The spacer pattern 140 or240 may be formed of individual spacers 145 or 245 formed on individualsides of the blocks of sacrificial material 136 or 236 of the pattern ofsacrificial material 135 or 235, and also sides of the blocks ofsacrificial material 339 of the additional sacrificial material pattern338. The spacer pattern 140 is formed by depositing the spacer materialon sides of the blocks of sacrificial material 136 making up the patternof sacrificial material 135 or 235, and then etching away excess spacermaterial from the buffer layer and the top surface of the block ofsacrificial material. The deposition may be done by a gas phase chemicalprocess such as atomic layer deposition. The etching may be performed byan anisotropic dry etching process. The etching process may cause a sideof the spacer 145 or 245 facing away from the block of sacrificialmaterial to have a slanted portion, slanting toward the block ofsacrificial material. Each of spacer 145 or 245 formed may have anaspect ratio of up to 18:1 or greater.

Process block 440 shows that the pattern of sacrificial material 135 or235 is removed. The pattern of sacrificial material 135 or 235 may beremoved by a wet etching process. The removal of the pattern ofsacrificial material 135 or 235 leaves the second openings 149 or 249open. Both the dry etching process and the wet etching process performedon the sacrificial material should not substantially etch the spacers145 or 245, the adhesive layer 208, the pattern of support material 205or the buffer layer 120 or 220.

Process block 450 shows that the array of color filters 150 or 250 andmicrolenses 160 or 260 are formed. The array of color filters 150 or 250may be formed in the first and second openings 148, 149 or 248, 249. Themicrolenses 160 or 260 may be formed on the array of color filters 150or 250.

FIG. 5 is a diagram illustrating one example of an imaging systemincluding a fully buried color filter array in accordance with theteachings of the present invention. As shown in the depicted example, animaging system 500 includes a pixel array 505 coupled to a controlcircuitry 535 and a readout circuitry 515, which is coupled to afunction logic 525.

Pixel array 505 is a two-dimensional (“2D”) array of pixels 507 (e.g.,pixels P1, P2 . . . , Pn). In one embodiment, each pixel is acomplementary metal-oxide-semiconductor (“CMOS”) imaging pixel. Pixelarray 505 may be implemented as either a front side illuminated imagesensor array or a backside illuminated image sensor array. In oneembodiment, pixel array 505 includes a fully buried color filter array,such as the fully buried color filter array depicted in FIG. 1G or 2H.The fully buried color filter array includes a plurality of buried colorfilters for the pixels 507. The fully buried color filter array may bearranged with pattern, such as Bayer pattern or mosaic of red, green,and blue additive filters (e.g., RGB, RGBG or GRGB), a color filterpattern of cyan, magenta, yellow, and key (black) subtractive filters(e.g., CMYK), a combination of both, or otherwise. As illustrated, eachpixel is arranged into a row (e.g., rows R1 to Ry) and a column (e.g.,column C1 to Cx) to acquire image data of a person, place, or object,which can then be used to render a 2D image of the person, place, orobject.

In one embodiment, after each pixel has acquired its image data or imagecharge, the image data is readout by readout circuitry 515 andtransferred to function logic 525. Readout circuitry 515 may includeamplification circuitry e.g., a differential amplifier circuitry,analog-to-digital (“ADC”) conversion circuitry, or otherwise.

Function logic 525 may include logic and memory for storing the imagedata or even manipulating the image data by applying post image effects(e.g., crop, rotate, remove red eye, adjust brightness, adjust contrast,or otherwise). In one example, the readout circuitry 515 may readout arow of image data at a time along readout column lines (illustrated) ormay readout the image data using a variety of other techniques (notillustrated), such as a serial readout or a full parallel readout of allpixels simultaneously.

Control circuitry 535 is coupled to pixel array 205. Control circuitry535 may include logic and memory for controlling operationalcharacteristic of pixel array 505. For example, control circuitry 535may generate a shutter signal for controlling image acquisition. In oneembodiment, the shutter signal is a global shutter signal forsimultaneously enabling all pixels 507 within pixel array 505 tosimultaneously capture their respective image data during a singleacquisition window. In an alternative embodiment, the shutter signal isa rolling shutter signal whereby each row, column, or group of pixels issequentially enabled during consecutive acquisition windows.

The above description of illustrated examples of the present invention,including what is described in the Abstract, are not intended to beexhaustive or to be limitation to the precise forms disclosed. Whilespecific embodiments of, and examples for, the invention are describedherein for illustrative purposes, various equivalent modifications arepossible without departing from the broader spirit and scope of thepresent invention. Indeed, it is appreciated that the specific examplevoltages, currents, frequencies, power range values, times, etc., areprovided for explanation purposes and that other values may also beemployed in other embodiments and examples in accordance with theteachings of the present invention.

These modifications can be made to examples of the invention in light ofthe above detailed description. The terms used in the following claimsshould not be construed to limit the invention to the specificembodiments disclosed in the specification and the claims. Rather, thescope is to be determined entirely by the following claims, which are tobe construed in accordance with established doctrines of claiminterpretation. The present specification and figures are accordingly tobe regarded as illustrative rather than restrictive.

What is claimed is:
 1. An image sensor, comprising: a substrate, whereinan array of photodiodes is disposed in the substrate; a plurality ofspacers arranged in a spacer pattern to form a spacer grid definingfirst openings; a buffer layer disposed between the substrate and thespacer pattern; an array of color filters disposed in the spacerpattern, wherein the plurality of spacers directly contacts colorfilters included in the array of color filters; and a pattern of supportmaterial structured to form a support material grid defining secondopenings overlapping with the first openings defined by the spacer grid,wherein the pattern of support material is disposed between the spacerpattern and the buffer layer, wherein the first openings of the spacergrid are wider than the second openings of the support material gridsuch that there is a lateral separation distance between edges ofindividual spacers included in the plurality of spacers andcorresponding edges of the pattern of support material where theindividual spacers interface with the pattern of support material,wherein proximal portions of the individual spacers included in theplurality of spacers extend from proximate to the pattern of supportmaterial, wherein distal portions of the individual spacers respectivelyextend from the proximal portions, and wherein each of the distalportions narrows to form a single distal end having a width less than acorresponding uniform width of the proximal portions.
 2. The imagesensor of claim 1, wherein the spacer pattern extends further from thebuffer layer than the array of color filters extends from the bufferlayer.
 3. The image sensor of claim 1 wherein at least one spacerincluded in the plurality of spacers has an aspect ratio of at least18:1.
 4. The image sensor of claim 1, wherein a thickness of each one ofthe plurality of spacers is less than or equal to 0.05 μm.
 5. The imagesensor of claim 1, wherein each of the color filters included in thearray of color filters is disposed in a respectively aligned one of thefirst openings and the second openings.
 6. The image sensor of claim 1,wherein each one of the plurality of spacers consists of a spacermaterial having a refractive index lower than a refractive index of eachcolor filter included in the array of color filters.
 7. The image sensorof claim 1, wherein a combined height of the spacer pattern and thepattern of support material is greater than a height of the array ofcolor filters.
 8. The image sensor of claim 1, wherein a portion ofsupport material included in the pattern of support material anddisposed between two adjacent second openings included in the secondopenings has a first width greater than a second width of an individualspacer included in the plurality of spacers.
 9. The image sensor ofclaim 1, wherein the pattern of support material further includes anadhesive layer disposed between the plurality of spacers included in thespacer pattern and a first support material included in the pattern ofsupport material to provide adhesion between the first support materialand the spacer pattern.
 10. The image sensor of claim 9, wherein theadhesive layer directly contacts the color filters included in the arrayof color filters.
 11. The image sensor of claim 1, further comprising amicrolens array, wherein each microlens included in the microlens arrayextends, at least in part, into a respective opening included in thefirst openings of the spacer pattern, wherein the array of color filtersis disposed between the buffer layer and the microlens array, andwherein the single distal end of the individual spacers are disposedbetween corresponding adjacent microlenses included in the microlensarray.
 12. An image sensor, comprising: a substrate, wherein an array ofphotodiodes is disposed in the substrate; a plurality of spacersarranged in a spacer pattern to form a spacer grid defining firstopenings; a buffer layer disposed between the spacer pattern and thesubstrate; an array of color filters disposed in the spacer pattern; anda pattern of support material structured to form a support material griddefining second openings, wherein the pattern of support material isdisposed between the spacer pattern and the buffer layer, wherein thefirst openings of the spacer grid are wider than the second openings ofthe support material grid such that there is a lateral separationdistance between edges of individual spacers included in the pluralityof spacers and corresponding edges of the pattern of support materialwhere the individual spacers interface with the pattern of supportmaterial, and wherein the first openings and the second openings definecavities at least partially filled by the color filters included in thearray of color filters, wherein proximal portions of the individualspacers included in the plurality of spacers extend from proximate tothe pattern of support material, wherein distal portions of theindividual spacers respectively extend from the proximal portions, andwherein each of the distal portions narrows to form a single distal endhaving a width less than a corresponding uniform width of the proximalportions.
 13. The image sensor of claim 12, wherein the pattern ofsupport material further includes an adhesive layer disposed between theplurality of spacers included in the spacer pattern and a first supportmaterial included in the pattern of support material, wherein theplurality of spacers directly contacts the color filters included in thearray of color filters.
 14. The image sensor of claim 12, wherein atleast one spacer included in the plurality of spacers has an aspectratio of at least 18:1, and wherein a thickness of the individualspacers included in the plurality of spacers is less than or equal to0.05 μm.
 15. The image sensor of claim 12, wherein each one of thesecond openings is positioned to overlap with a corresponding one of thefirst openings formed by the plurality of spacers included in the spacerpattern.
 16. The image sensor of claim 15, further comprising amicrolens array, wherein each microlens included in the microlens arrayextends, at least in part, into a respective opening included in thefirst openings of the spacer pattern, wherein the array of color filtersis disposed between the buffer layer and the microlens array, andwherein a combined height of the spacer pattern and the pattern ofsupport material is greater than a height of the array of color filterssuch that the single distal end of the individual spacers are disposedbetween corresponding adjacent microlenses included in the microlensarray.
 17. The image sensor of claim 12, wherein the pattern of supportmaterial further includes an adhesive layer disposed between theplurality of spacers included in the spacer pattern and a first supportmaterial in the pattern of support material, wherein the adhesive layerand the first support material are both etch selective with respect tothe buffer layer.
 18. The image sensor of claim 12, wherein the patternof support material directly contacts the color filters included in thearray of color filters.
 19. The image sensor of claim 12, wherein theplurality of spacers have a composition consisting of a spacer materialhaving a refractive index of 1.3 or less.
 20. The image sensor of claim12, wherein a first pair of the single distal end of a first pair ofspacers included in the plurality of spacers that are adjacent to oneanother are slanted towards each other.